Unexpected regiochemistry in the reaction of benzotriazole with KBH4: synthesis of a new class of poly(azolyl)borate ligands

Lalor, Fergus J.; Miller, Stefan M; Garvey, N.

doi:10.1016/0022-328x(88)83101-2

Cited by 20 publications

(6 citation statements)

References 12 publications

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“…Boron substitution at the triazole N(1) atom is more sterically demanding for Tp′, being first proposed in homoscorpionates of benzotriazole, HB(Btz) 3 , based on IR measurements. 41 In the present structure for cis-Fe(Tp′) 2 this boron-substitution mode is confirmed. In 1988 Lalor et al and in 1994 Calogero et al 42 also noted the feasibility of the "extra" free triazole N(3) atoms acting as donors to additional Lewis acid centers.…”

Section: Solid-state Xrd Structures Of Cis-fe(tp′) 2 and Itssupporting

confidence: 71%

Rational Design of Iron Spin-Crossover Complexes Using Heteroscorpionate Chelates

et al. 2022

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The optical, structural, and magnetic properties of iron(II,III) sandwich complexes, Fe(Tp′)2 n+ (Tp′ = bis(3,5-dimethylpyrazolyl)benzotriazolylborate), are described. The intensely colored FeII(Tp′)2 (orange) and FeIII(Tp′)2 + (purple) show strong MLCT bands. Geometric isomerism for M(Tp′)2 is established crystallographically in the racemate of chiral cis-Fe(Tp′)2. For the first time, paramagnetic 11B NMR describes solution-phase low-spin (LS, S = 0) to high-spin (HS, S = 2) crossover behavior in Fe(Tp′)2. Thermochemical parameters for solution-phase SCO of Fe(Tp′)2 demonstrate the endothermic LS to HS conversion and entropic preference of the HS state. Entropy changes for both Fe(Tp′)2 isomers are significantly larger than for the majority of iron scorpionate SCO systems. Solid-state magnetic and thermochemical measurements show cis-Fe(Tp′)2 to be thermally stable up to 520 K, allowing experimental investigation of a solid-state SCO magnetic hysteresis of over 45 K. A large solution vs solid-state SCO difference was observed: cis-Fe(Tp′)2 shows T c ≈ 270 K (solution) and T c ≈ 385 K (solid), with the remarkably wide ΔT c ≈ 115 K; trans-Fe(Tp′)2 shows T c ≈ 278 K (solution) and T c ≈ 372 K (solid). Solid-state T c values are among the highest seen for iron(II) molecular systems. The large solution/solid ΔT c difference is explained by “anchoring” intermolecular interactions in the solid state that prevent thermal expansion of the LS iron(II) coordination sphere in its transition to the HS state. DFT calculations, validated against LS cis-Fe(Tp′)2 crystallography and LS to HS SCO thermochemical parameters, demonstrate the role the benzotriazole rings play in its structural and optical properties. The Lewis basicity of M(Tp′)2 is shown with the structural characterization of the air-stable tin(II) adduct [cis-Fe(Tp′)2-SnCl2]; tin(II) coordination does not alter the iron(II) spin state. The Tp′ chelate adds functionality (asymmetry, chirality, chemical reactivity) to the array of iron SCO materials for potential incorporation into nanoscale magnetic switches and spintronic devices.

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Section: Solid-state Xrd Structures Of Cis-fe(tp′) 2 and Itssupporting

confidence: 71%

Rational Design of Iron Spin-Crossover Complexes Using Heteroscorpionate Chelates

et al. 2022

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“…Those complexes are much more soluble than their Tp* counterparts, especially in polar media (alcohols and DMF, but not water) . Transition metal complexes of benzotriazole-containing homoscorpionates (like hydrotris(benzotriazolyl)borate) show generally poor solubilities in organic solvents. , Similarly poor solubility is seen with (Tp*) 2 Ni in most organic solvents.…”

Section: Resultsmentioning

confidence: 99%

“…Benzotriazole (btz) is a common nitrogen-containing heterocycle that has been attached to a variety of polystyrene resins, , making it the likely candidate for Strategy III. Homoscorpionates based on 1,2,4-triazoles and 1,2,3-benzotriazoles and their transition metal complexes are known, and traditionally synthesized via standard high temperature reactions with sodium or potassium borohydride in excess molten heterocycle, as was first established by Trofimenko more than 40 years ago . For the purpose of Strategy III, the ability of benzotriazole to mimic the behavior of pyrazole when bound to boron was key.…”

Section: Introductionmentioning

confidence: 99%

Immobilized Boron-Centered Heteroscorpionates: Heterocycle Metathesis and Coordination Chemistry

et al. 2010

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The preparation of a resin-supported boron-scorpionate ligand and its nickel(II) coordination complexes are reported. The supported ligand is prepared as its potassium salt, making it a general reagent suitable for chelation of any transition metal ion. Resin-immobilized benzotriazole (Bead-btz) reacted cleanly with KTp* (Tp* = hydrotris(3,5-dimethylpyrazolyl)borate) by heterocycle metathesis in warm dimethylformamide (DMF) to yield bead-Tp'K, {resin-btz(H)B(pz*)(2)}K. Significantly, bead-Tp'K readily bound nickel(II) from simple salts with minimal leaching of the nickel ion. Bead-Tp'NiNO(3) reacts further with cysteine thiolate (ethyl ester), imparting the deep green color to the beads characteristic of a Tp(R)NiCysEt coordination sphere. Bead-Tp'NiCysEt exhibited an oxygen sensitivity similar to Tp*NiCysEt in solution (Inorg. Chem. 1999, p 5690) and also independently verified for a selenocystamine analogue, Tp*NiSeCysAm. Addition of fresh cysteine thiolate ethyl ester to oxidized bead-Tp'NiCysEt reproduced the original green color. Heterocycle metathesis was also used to prepare KTp' as a white solid. Reaction with nickel(II) gave (Tp')(2)Ni, separable into two different isomers. The air-sensitive molybdenum(0) complex, [PPh(4)][Tp'Mo(CO)(3)], was also prepared and the C(s) complex symmetry demonstrated by infrared and (13)C NMR spectroscopies. Immobilized TpmMo(CO)(3) was prepared from the previously reported resin-supported tris(pyrazolyl)methane. In contrast to its weak coordination of nickel(II) (Inorg. Chem. 2009, p 3535), bead-Tpm proved a strong chelate toward this second row metal. The supported scorpionates described here should find use in studies of selective metal-protein binding, metalloprotein modeling, and heterogeneous catalysis, and render such scorpionate applications amenable to combinatorial methods.

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“…1 : In the IR spectra of complexes 1, 2, 4, 5, 7 and 8, the characteristic band for the stretching vibration of B−H bond is observed in the region 2450-2530 cm −1 , and the corresponding wavenumber values are shifted to higher frequencies with respect to those of the free ligands Tp 4Bo,5Me and Tp a ( Figure S1, Supplementary Information) [33]. In the region 2800-3000 cm −1 there are signals of weak or medium intensity, which are assigned to the stretching of methyl C−H bonds from Tp 4Bo,5Me and ethylenic -CH 2 CH 2 − bonds (tethering group) from Tp a .…”

Section: Synthesis and Characterizationmentioning

confidence: 99%

Synthesis, Characterization and Assessment of the Antioxidant Activity of Cu(II), Zn(II) and Cd(II) Complexes Derived from Scorpionate Ligands

et al. 2020

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Seeking to enrich the yet less explored field of scorpionate complexes bearing antioxidant properties, we, here, report on the synthesis, characterization and assessment of the antioxidant activity of new complexes derived from three scorpionate ligands. The interaction between the scorpionate ligands thallium(I) hydrotris(5-methyl-indazolyl)borate (TlTp4Bo,5Me), thallium(I) hydrotris(4,5-dihydro-2H-benzo[g]indazolyl)borate (TlTpa) and potassium hydrotris(3-tert-butyl- pyrazolyl)borate (KTptBu), and metal(II) chlorides, in dichloromethane at room temperature, produced a new family of complexes having the stoichiometric formula [M(Tp4Bo,5Me)2] (M = Cu, 1; Zn, 4; Cd, 7), [M(Tpa)2] (M = Cu, 2; Zn, 5; Cd, 8), [Cu(HpztBu)3Cl2] (3), [Zn(TptBu)Cl] (6) and [Cd(BptBu)(HpztBu)Cl] (9). The obtained metal complexes were characterized by Fourier transform infrared spectroscopy, proton nuclear magnetic resonance and elemental analysis, highlighting the total and partial hydrolysis of the scorpionate ligand TptBu during the synthesis of the Cu(II) complex 3 and the Cd(II) complex 9, respectively. An assessment of the antioxidant activity of the obtained metal complexes was performed through both enzymatic and non-enzymatic assays against 1,1-diphenyl-2-picryl- hydrazyl (DPPH·), 2,2′-Azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS+·), hydroxyl (HO·), nitric oxide (NO·), superoxide (O2−) and peroxide (OOH·) radicals. In particular, the complex [Cu(Tpa)2]⋅0.5H2O (2) exhibited significant antioxidant activity, as good and specific activity against superoxide (O2−·), (IC50 values equal to 5.6 ± 0.2 μM) and might be identified as auspicious SOD-mimics (SOD = superoxide dismutase).

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Unexpected regiochemistry in the reaction of benzotriazole with KBH4: synthesis of a new class of poly(azolyl)borate ligands

Cited by 20 publications

References 12 publications

Rational Design of Iron Spin-Crossover Complexes Using Heteroscorpionate Chelates

Rational Design of Iron Spin-Crossover Complexes Using Heteroscorpionate Chelates

Immobilized Boron-Centered Heteroscorpionates: Heterocycle Metathesis and Coordination Chemistry

Synthesis, Characterization and Assessment of the Antioxidant Activity of Cu(II), Zn(II) and Cd(II) Complexes Derived from Scorpionate Ligands

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